1. Technical Field of the Invention
The present invention relates generally to a control system designed to control an operation of an air conditioner and/or a generating motor in vehicles.
2. Background Art
Typical electric vehicles are not equipped with a combustion engine and thus are usually engineered to control an air conditioner in a cabin using a device such as PTC (Positive Temperature Coefficient) heater or an electric compressor which works to convert electric power of a vehicle-driving battery into heat. The activation of the air conditioner, therefore, results in a decrease in amount of charge in the vehicle-driving battery, which will lead to a decrease in cruising distance (also be called a distance-to-empty) of the vehicle.
Usually, when left unused for a long time, the vehicle-driving battery is self-discharged, thus causing the vehicle to be likely to be disabled.
There are known series-hybrid vehicles equipped with a vehicle-driving battery, a driving electric motor, a power generating engine, and a power generating electric motor. The series-hybrid vehicle work to drive the power generating electric motor using the power generating engine to supply electric power required to run the vehicle to the vehicle-driving motor and also to deliver an excess of the electric power to the vehicle-driving battery.
When the amount of electric energy remaining in the vehicle-driving battery (i.e., State Of Charge) is low, the series-hybrid vehicles need to secure the electric power required to run the vehicle only by means of the power generating engine. It is, thus, necessary to use the power generating engine and the power generating electric motor which are capable of producing a large amount of electric power.
The series-hybrid vehicles need to change the output of the power generating engine as a function of load on running them (which will also be referred to as a running load below). Accordingly, in the case where the power generating engine is implemented by an internal combustion engine, it will result in a decrease in fuel economy. Additionally, the output of the power generating engine (i.e., a driven condition of the vehicle) is, as described above, changed as a function of the running load, thus resulting in instability of the temperature of the power generating engine. It is, thus, difficult to effectively use the power generating engine as a power source for the air conditioner. For instance, it is difficult to utilize the thermal energy, as produced by the power generating engine, for air heating through the air conditioner.
Japanese Translation of PCT application, as listed below, teaches techniques for installing an auxiliary driving device for supplying the energy to an air conditioning system to heat a working fluid flowing through a heater core and controlling operations of an evaporator, a compressor, and a condenser.    Japanese Translation of PCT application No. 2006-525899
The electric vehicles, as described above, face the problem that the activation of the air conditioner results in a decrease in distance-to-empty of the vehicle. In order to alleviate such a problem, vehicles, such as the series-hybrid vehicles equipped with the power generating engine, may be designed to use the power generating engine for operating the air conditioner. However, the series-hybrid vehicles, as described above, usually change the engine power as a function of the running load, and thus encounter the problem of a decrease in fuel economy. The change in engine output also results in a difficulty in effectively utilizing the power generating engine as a power source for the air conditioner. Further, the series-hybrid vehicles require large-sized engine and generating motor.
The above publication only teaches activating the auxiliary drive device to supply the energy to the air conditioning system and is silent about control of the auxiliary drive device depending upon an operating condition of the vehicle. It is, therefore, impossible for the system, as disclosed in the above publication, to solve the problems from which the electric vehicles or series-hybrid vehicles suffer.
It is an object of the invention to provide a control system for a vehicle equipped with an engine for actuating an air conditioner which is designed to ensure stability in operation of the engine.